A device that is capable of writing data to and reading data from an optical storage media (e.g., a CD or DVD) typically includes a light source and a light detector (also known as an optical pickup). During writing, data is imparted on the media in the form of “bumps” and “lands,” which reflect light differently. During reading, the light source, e.g., a laser diode, produces a source light signal that is directed toward the media such that light reflected from the media is modulated with the data stored on the media. The light detector, e.g., one or more photodetectors, detects the light reflected from the media, with the output of the light detector being a data signal. The data signal is typically amplified by a preamplifier before the data signal is provided to an analog to digital converter, etc.
In the past, noise cancellation schemes have primarily focused on reducing noise that is produced at an input stage to the preamplifier, without concern for noise from the light source. However, as data speeds increase, the noise from the source is becoming a more significant portion of the overall noise, approaching the same order of magnitude as the noise from the input stage. Additionally, the next generation of optical storage devices will use blue laser diodes, which are much noisier that conventional laser diodes. Accordingly, there is a need to reduce, and preferably cancel noise from the source.